1. Field of the Invention
The device of this invention resides in the field of electrical testing devices and more particularly relates to the determination of the electrical condition of overhead lines and third rail lines for direct current electrical railway systems, such device including a multiple LED warning light with built-in volt meter and optional audio alarm to provide multiple indications as to the energized state of such overhead lines and third rail lines.
2. Description of the Prior Art
Determining the energized state of overhead lines and third rail lines for an electrically operated rail line for direct current has been heretofore carried out by very basic devices and methods. One approach is a series of incandescent lamps which light or not depending upon the presence of power in the line. The incandescent light bulbs are used in a series circuit so that a voltage drop across each bulb would be equal to the rated voltage of such bulb. For example, a 600 volt line would use five bulbs in series, referred to as a five-light cluster, so that a voltage drop of approximately 120 volts would be achieved. There are many problems with five-light clusters in that the voltage functionally caused the bulbs to glow brightly, as the voltage increased, or dimly, as the voltage decreased. These voltage changes tend to weaken the filaments in the bulbs; and such filaments, when broken in one of the bulbs in the series of five, cause an open circuit, thus causing the other four bulbs to go dark. This situation would create a false indication of the voltage in the lines being tested which the user of the five-light cluster would wrongly assume were de-energized. Trouble shooting a five-light cluster is difficult as each old bulb has to be removed and a new bulb substituted therefor until the defective bulb could be found. Such need for substitution of bulbs also required having spare bulbs always available on site. Users of the five-light clusters are further usually unable to prevent vibrations and shock damage to the five-light clusters during their transportation to the work site. Such vibrations and shocks cause the filaments of the bulbs to weaken or break and can cause the glass globes of the bulbs to break, further increasing the unreliability of the five-light cluster. One improvement made over the five-light cluster is the use of a single incandescent bulb in an electrical series circuit with a resistor to provide a voltage drop. The advantage of the use of such single incandescent bulb over the five-light cluster is that only one bulb needs to be changed when the bulb fails, but the light output is greatly diminished due to its having only one light rather than five. A further disadvantage is that heat is generated from the resistor.
The prior art incandescent warning devices can be either attached by hand wiring to the lines being tested such as being fixed in a permanent location, or such devices can be placed on a long pole with a metal hook at one end. The metal hook can be mounted on a wooden pole and placed on a messenger wire up to 25 feet above the track. However, such devices are heavy and cumbersome, and some workers encounter much difficulty in raising the pole and hooking it to the wire.
Another method of determining the energized state of overhead lines and third rail lines is the hand use of a voltmeter to read line voltage at disconnect switches. Voltmeters can also be attached to a pole with such a metal hook as previously described wherein the voltage would pass from the metal hook down a wire to the voltmeter. In some cases rather than a hook with a wire leading to the voltmeter, a ladder is placed against the wires and a worker would climb up and put the positive wire lead against the messenger and contact wires for one connection. The negative wire lead of the voltmeter would then be connected to the running rail to complete the circuit to give an indication of the voltage level on the lines being tested. Such voltage measuring procedures do not provide for the safer remote indication of the voltage since the person reading the voltmeter""s voltage display must be in a proximate location to the device in order to read it.
Thus, the prior art requires either climbing a support pole for hand checking with a voltmeter, or the use of fragile and somewhat unreliable incandescent light bulbs which bulbs in particular are subject to globe breakage or filament breakage from changing temperatures, environmental vibrations, movement by the user or just wearing out.
In contrast, the present invention provides a safe, reliable and accurate system for determining the power status of overhead lines and third rail lines which system can be used at ground level without the need for climbing a support pole or subjecting the user to being in close proximity to the lines being tested.
The invention may be summarized as a voltage testing apparatus for determining the power condition of overhead lines and third rail lines, such invention consisting of a telescopic pole, a voltage indicator, a ground connection device such as a transport rail attachable magnet, and connection wires to provide an electrical circuit between the cable, indicator and ground.
The indicator is mounted on the pole which may be extendible and retractable and has an electrically conducting cable engaging device, such as a hook mounted on one end. A wire connects the hook and indicator, and another wire connects the magnet and indicator. When the magnet is placed on the running rail and the hook is lifted to and either placed on the overhead line, a circuit is created which will establish the power status of the cable. On a third rail system the wire to the hook can be disconnected therefrom and attached to a second magnet to be adhered to the voltage-carrying power rail of a third rail line.
Thus it is an object of this invention to provide an easily visible, audible and easily readable digital voltage display device that provides an indication of the electrical condition of messenger and contact wires, contact rails and the power rail of a third rail line as utilized on electrical railway systems, with LED warning lights providing a highly visible warning to any workers to avoid coming into direct contact with the electrical wires and conductors that are energized with voltage. The array of LED warning lights are connected in an electrical series circuit with a plurality of such circuits connected in parallel with one another so as to create, when illuminated, an intensely bright display capable of being seen even in direct sunlight. Even if one or more LEDs should burn out, the other interconnected strings of LEDs are not affected, and the unit will continue to provide a very bright display even in the event of numerous LED string burn outs. Further the strings of LEDs are arrayed within a clear plastic globe housing in a 360-degree circle so that they are visible from all directions. The clear plastic globe provides complete and total encapsulation so as to protect the LEDs and other components from impact, moisture and other damage that prior art systems are exposed to.
The indicator can include an array of LEDs, a voltmeter and an audible alarm. The indicator can also be enclosed in such clear plastic globe housing for the protection of the user against shock and to protect the indicator from the environment. The LED array can be multisided to provide for observation from a variety of horizontal positions and the housing transparent to allow such observation. Further, different colors of LEDs can be used to indicate different power conditions, for example, red for power and green for no power. Finally, a nonconductive handle can be attached to the magnet to assist in its placement and removal and for safety for the user against shocks. Alternatively, a ground contact can be provided by a second hook disposed at the same end of the pole as the first hook to simultaneously engage an overhead ground cable. The digital voltmeter is positioned on the top of the LED array and is actuated by pressing a button on the lower side of the device to give an indication of the actual voltage on the electrical power lines being tested. The voltmeter can also provide a circuit integrity test to determine whether the indicator is functioning properly. The voltmeter is powered by a replaceable 9-volt battery installed in the base of the housing of the device of this invention. The housing of the device of this invention can be made of high impact-resistant, non-electrically conducting plastic which will absorb shock should the device be dropped or struck. The transparent globe housing can be unscrewed from the lower base to gain access to the LED array. The LED array is removable from the housing to gain access to the voltmeter battery. The lower part of the housing is constructed with four threaded knockout openings for the installation of electrical connectors, bushings or tubings, such openings being situated 90-degrees apart around the base which is generally cylindrical in configuration. One of the openings allows the positive and negative wires that are measuring the power to be directed to the LED array. The bottom of the base is flat for easy mounting on surfaces or on other components. The audio warning device can be a horn with a loudness level of 120 decibels at 600 volts. The horn speaker can be internally located in an opening on a side of the housing.
The digital voltmeter can be located on top of the digital array facing upwards and visible through the clear plastic housing. The voltmeter can be activated by a test button located on the side of the housing.
These and other features and advantages of the invention will become more apparent from the description of the preferred embodiment(s) and drawings which follow.